1. Field of the Invention
The present invention relates to a method for cleaning a device to form a film made from carbon or containing carbon as a main ingredient.
2. Description of the Prior Art
Conventionally, a carbonaceous film, that is a film made from carbon or containing carbon as a main ingredient, has superior resistance to abrasion, a high degree of smoothness, superior insulation characteristics, and superior resistance to chemicals, and the like, so that its practical application as a material having a wide variety of characteristics is expected. Coating technology for the carbonaceous film is known, for example, Japanese Laid Open Patent Application No. Sho-56-146930.
However, it is difficult to use the same deposition chamber many times to form such carbonaceous films because of problems such as vacuum reduction and flaking. After one or two cycles of forming the film, it becomes necessary to clean the inside of the deposition chamber. The gases which are used in conventional cleaning are, for example, hydrogen, oxygen, or gaseous fluoride for cleaning the solid film containing carbonaceous ingredients since a volatile gas is made in a plasma reaction with the carbonaceous ingredients. What is meant by the plasma reaction here is a reaction in which a plasma of hydrogen, oxygen or gaseous fluoride is formed for the reaction with the carbonaceous ingredients.
The technology of etching a carbonaceous film gives rise to difficult problems in the practical application to products of the carbonaceous film. For example, in a method of etching by carrying out a hydrocarbon type gasification reaction of the carbonaceous film with hydrogen to produce C.sub.X H.sub.Y or the like, the fouling of the inside of the deposition chamber is reduced, but, many problems occur due to the low etching velocity from the aspect of mass production velocity.
On the other hand, O.sub.2 is the most convenient gas for use in plasma etching of the carbonaceous film, the greater part of which is exhausted in the form of CO, CO.sub.2, and the like. However, part of the O and O.sub.2 not to be reacted or CO and CO.sub.2 remains on the inner walls. When the carbonaceous film is formed after a conventional cleaning, these gaseous ingredients tend to break away from the inner walls to diffuse in the vapor phase, resulting in auto-doping inside the film, or being trapped at the interface. Accordingly, the film quality and interface characteristics (particularly adhesion characteristics) deteriorate.